Known in the past has been an internal combustion engine provided with a variable compression ratio mechanism which can change a mechanical compression ratio of the internal combustion engine. As such a variable compression ratio mechanism, various mechanisms have been proposed. As one among these, one which can change the effective length of a connecting rod used in the internal combustion engine may be mentioned (for example, PTLs 1 and 2). In this regard, the “effective length of a connecting rod” means the distance between a center of a crank pin receiving opening which receives a crank pin and a center of a piston pin receiving opening which receives a piston pin. Therefore, if the effective length of a connecting rod becomes longer, a combustion chamber volume when the piston is at top dead center of the compression stroke becomes smaller, and therefore the mechanical compression ratio increases. On the other hand, if the effective length of a connecting rod becomes shorter, the combustion chamber volume when the piston is at top dead center of the compression stroke becomes larger, and therefore the mechanical compression ratio falls.
As a variable length connecting rod which can be changed in effective length, known is one which is provided with a connecting rod body with a small end on which an eccentric member (eccentric arm or eccentric sleeve), which can swivel with respect to the connecting rod body, is provided (for example, PTLs 1 and 2). The eccentric member has a piston pin receiving opening which receives the piston pin. This piston pin receiving opening is provided so as to offset with respect to a swivel axis of the eccentric member. In such a variable length connecting rod, if changing the swivel position of the eccentric member, the effective length of the connecting rod can be changed accordingly.